Big drug companies have sought to strike mergers to strengthen their product lineups as patents expire, in what analysts have called a ''patent cliff.'' Late next year, Pfizer is set to lose the patent on one of its most lucrative drugs, the cholesterol fighter Lipitor.

About $42.2 billion worth of pharmaceutical deals have been struck so far this year, according to data from Thomson Reuters. That number is close to the $45.8 billion in pharmaceutical mergers announced by the same time last year, excluding Pfizer's blockbuster Wyeth deal and Merck's $41 billion purchase of Schering-Plough.

In King, Pfizer is gaining a variety of businesses that complement its own offerings. Among the most attractive are pain medications like Embeda, a strong drug that is engineered to be more resistant to patient abuse, and Flector, a medicinal patch. It is also working on other drugs like Remoxy, an oxycodone drug that is meant to be more abuse-resistant than OxyContin.

Pfizer already makes pain drugs like Lyrica and Celebrex.

''We'll continue to stay focused in the areas we do business in,'' Frank D'Amelio, Pfizer's chief financial officer, said on an analyst conference call on Tuesday. ''We really want to stay focused in the areas that we've talked about before and really stay I'll call it in our core space, which is what we believe we do best.''

King also makes products like the EpiPen emergency drug injector and a variety of animal health drugs, further complementing its buyer's offerings.

Pfizer said that the deal would yield at least $200 million in savings through 2013, a figure that UBS research analysts said on Tuesday was ''very conservative.'' The deal is expected to close by the first quarter next year.

Analysts praised the deal. Barbara Ryan of Deutsche Bank described it in a research note as a ''disciplined, but not 'sexy' acquisition.''

Of King's products, Jami Rubin of Goldman Sachs wrote in a note on Tuesday: ''These assets may potentially perform better under Pfizer's umbrella, in our view, given Pfizer's strong marketing machine.''

Pfizer executives said on a conference call Tuesday that the company will continue to pursue bolt-on deals that supplement its existing businesses. The company still has plenty of buying firepower: it reported $19.3 billion in cash and short-term investments as of July 4.

King is no stranger to deal-making: it pursued a months-long hostile bid for Alpharma in 2008, eventually raising its offer to $1.5 billion from $1.4 billion to seal the merger. It was through Alpharma that King gained Embeda.

Pfizer was advised by JPMorgan Chase and the law firm Cadwalader, Wickersham & Taft. King was advised by Credit Suisse and the law firm Covington & Burling.

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